Teaching Case

An elderly man presented with a painless, firm-consistency midline swelling of the anterior abdominal wall in the epigastrium. His past medical history included diabetes, hepatitis B-virus-related chronic liver disease, radical prostatectomy and lymphadenectomy for prostatic carcinoma. Twenty months earlier, he had a partial left hepatectomy for hepatocellular carcinoma (HCC).

Twenty months earlier, multidetector CT (Fig. 1) showed a 5x3.5 cm well-demarcated, lobulated subcapsular mass in the left liver lobe, with early hyperenhancement, subsequent contrast washout, and a central hypoattenuating scar-like area. Fine-needle aspiration biopsy (FNAB, Fig. 2) diagnosed HCC.
After partial left hepatectomy (normal early postoperative CT appearance in Fig.3), histopathology confirmed trabecular HCC not involving the resection margins. Follow-up CT 6 months after surgery (Fig. 4) excluded signs of local or distant recurrence.
Currently, increased (1547 ng/ml) alpha-fetoprotein suggested HCC recurrence. Repeated CT (Fig. 5) showed a round 8 cm median solid mass centred in the epigastric subcutaneous fat, with heterogeneous hypervascularization and "mosaic" washout, without signs of liver or distant HCC recurrence.
After surgical excision (postoperative CT in Fig. 6), histopathology confirmed diagnosis of recurrent trabecular HCC from neoplastic seeding along the previous FNAB needle track.
Four months later, lung metastases (Fig. 7) appeared, without recurrent HCC in the liver and along the previous needle track.

In patients with hepatocellular carcinoma (HCC), needle-track tumour seeding (NTNS) is an uncommon but important complication of percutaneous diagnostic and therapeutic procedures such as biopsy (either with aspiration or end-cutting needles), ethanol injection and radiofrequency ablation. Defined as new neoplastic disease arising outside the liver capsule (either in the subcutaneous tissue or peritoneal cavity), NTNS develops after a median 10 months from needle biopsy and/or local ablative therapy, sometimes after liver transplantation. The risk is higher with diagnostic biopsy (1.6-3.4%) compared to therapeutic procedures (ethanol injection 1.4%, radiofrequency ablation 1-2.5%). Other risk factors include large tumour size, poor histological differentiation, number of needle passes and thickness of liver parenchyma overlying HCC [1-6].
Although accepted as a safe, accurate minimally invasive diagnostic technique, ultrasound-guided fine-needle aspiration biopsy (FNAB) of HCC is controversial due to the potential risk of NTNS, particularly in patients being considered for liver transplantation. According to the European Association for the Study of the Liver (EASL) guidelines HCC is often treated without prior histological confirmation in patients with consistent imaging and laboratory features. While imaging currently obviates the need for tissue sampling in most patients, biopsy may be sometimes required for diagnostic confirmation or differentiation from other neoplastic or tumour-like lesions [1, 5-7].
As this case exemplifies, NTNS presents with palpable nodules in the location of the previous biopsy tract or with raising serum tumour markers, sometimes years after ablative or surgical treatment of HCC. Therefore, the possibility of thoracic-abdominal wall implants should be considered during interpretation of cross-sectional imaging studies in patients with history of percutaneous diagnostic procedures and/or ablation therapy. CT findings of NTNS include circumscribed oval or round nodules (usually measuring 1-6 cm) located along the needle tract, mostly in the subcutaneous fat (with or without skin involvement) or the intercostal muscle layers. The CT features resemble those of the original biopsied or ablated HCC, including basal soft-tissue attenuation similar to the abdominal wall muscles, hyperenhancement on hepatic arterial phase and iso-hypodensity in equilibrium phase [2, 3, 5, 8].
Indications for surgery for implanted HCC include: a) limited number of lesions, b) intrahepatic lesions absent or predicted to be locally controllable, and c) sufficient hepatic functional reserve. After surgical excision, repeated NTNS may occur in 25% of patients. Following effective treatment by en-bloc wide resection, NTNS does not significantly alter the long-term prognosis, which is related to intrahepatic HCC progression and hepatic failure [7, 9].